Effect of Spray Angle on Temperature Distribution within the Metallic Substrate in Cold Spraying

This study investigates the effect of spray angle on the temperature distribution within the metallic substrate in cold spraying. Computational fluid dynamic approach is employed in this work to achieve this objective. The simulated results show that spray angle significantly influences the temperature distribution within the substrate. For the perpendicular spraying, the temperature gradient contours present regularly annular shape, which means the temperature distribution is only dependent on the radial position. Furthermore, the peak value of the surface temperature is not at the geometric center (stagnation point) but at the position slight away from the center, which may result from the transition of the flow from laminar to turbulent state. Along the radial direction, there exists a secondary peak of the temperature arising from the expansion waves in the adherence jet. With decreasing the spray angle, the secondary peak in the uphill direction disappears. But in the downhill direction, the secondary peak still exits and the distance from the geometric center increases with the decrease in spray angle. In addition, the temperature distribution within the substrate indicates that the residual tensile stress inside the substrate mainly exists near the front zone, but for the angular spraying at the uphill direction, it appears near the back surface. Besides, the simulated results indicate that the best way to preheat the substrate at the angular condition is to move the nozzle from uphill toward the downhill direction.